Hello again, a few weeks back I posted some questions about the VCA. Al the questions are anwsered and it is working like a charm. I also made 2 ADSR modules, 1 worked right away, the other one burned himself because of a solder bridge between the ground and the negative side xD

To the point. Today i'm going to start to work on the Steiner VCF. Etching the PCB drilling the holes. The simple things. I only got a few questions about some values of resistors and 1 potentiometer.

R11 must be a 380 ohm resistor. I couldnt find that value which seems very strange to me. Does it exist?

R1, R2, R17 needs to be 10k or it has to be adjusted to some other value. Is the basic value of 10k good enough?

I couldn't find a 2.5K Trimmer. Which other value do I need? 2K or 5K?

The resonsnce pot doesn't have a value. I ordered a 25k lin potentiometer. Will it work? Is the range good enough?

Yves, Thanks for your reply. You helped me with this once again. I guess there is one thing I mixed up. The trimmer was something I could find. But the 2.2k or 2.5k lin potentiometer was the thing I couldn't find.

Also in your BOM there are only 4 potentiometers listed. I guess there need to be 5 of them.

The trimming should be quite easy according to the page. But when do you know when you've got a good v/oct tracking. Is there a way to measure it?

1 more thing. I decided to build the MiniMoog filter at first. I'm almost done with the PCB, matched the trannies by Hfe on my multimeter (hope it will do) but there is something i need to ask. How to match the 47nF capacitors. I know you can do it with a good DMM, but I don't have one. Is there another way?

Alright one more question. If I'm ready to trim the MiniMoog VCF, what node do I need to measure exactly? The middle node from the trannie to the 100pf capacitor? I'm not sure how to interpret the sentence.

Yves, Thanks for your reply. You helped me with this once again. I guess there is one thing I mixed up. The trimmer was something I could find. But the 2.2k or 2.5k lin potentiometer was the thing I couldn't find.

Also in your BOM there are only 4 potentiometers listed. I guess there need to be 5 of them.

The trimming should be quite easy according to the page. But when do you know when you've got a good v/oct tracking. Is there a way to measure it?

Here one is not looking for a perfect/accurate V/Oct tracking, as it is said for
the minimoog filter :
Set the filter to oscillation mode
Play a tune and check the goodness of the tracking
Slightly adjust the trimmer to achieve a good chromatic tracking (check by ear).

Otherwise you can use an electronic tuner for keyboards.

Quote:

1 more thing. I decided to build the MiniMoog filter at first. I'm almost done with the PCB, matched the trannies by Hfe on my multimeter (hope it will do) but there is something i need to ask. How to match the 47nF capacitors. I know you can do it with a good DMM, but I don't have one. Is there another way?

Not really simple but you may use sinusoidal generator and connect a 10K resistor and the cap in series at the output of the generator. Next set the frequency of the generator to 500 Hz and measure (in AC mode) the voltage at the legs of the capacitor. You must then select the capacitors that give you the same voltage within 1% tolerance.

Quote:

Alright one more question. If I'm ready to trim the MiniMoog VCF, what node do I need to measure exactly? The middle node from the trannie to the 100pf capacitor? I'm not sure how to interpret the sentence.

Hope you can help me again. Thanks already

That's correct the node that is common to the 100pF cap, R9 (1.8K) and R11 (100K) ._________________Yves

Alright, can figure that out now thanks. 1 more thing. P3 the resonant pot must be a 2.2K or a 2.5K potentiometer. I can't find it anywhere. The only values I can find are 2K or 5K. I'm using alpha potentiometers through my whole synth. Which value should I use?

Etched a board for this filter, and building it today, but it is the 2sc1583 version. At first startup i got some wonkiness, resonance wasn't working. And then i noticed this filter also has allpass response and needs a 4 position rotary [facepalm], didn't have a tl071 so put in 5534, but i have some lf355 and that's in now.
It seems to work for the most part though, did you get yours working Aottens?

Hi,
I have the same problem as mentioned by Aottens before.
Very low output with highpass and bandpass and very very ineffective cutoff control.
Lowpass gives a loud signal but seems to be completely unfiltered with no effect when turning the cutoff pot.
I did a layout by myself, omitted the buffer amps and swapped the rotary switch for a three-way-switch, since I don´t need allpass-mode.
Checked everything twice and couldn´t find a mistake.
Any idea someone?Last edited by El Mop on Fri Dec 07, 2012 4:12 pm; edited 1 time in total

I´ve built the 2SC1583 version with yet unmatched 2N3904.
I just figured out that I used 82K instead of 82R for R18!
I will give it a try a with a 510R and 100R in parallel since a lack of a 82R resistor and will report then.

Hi there. first of all, thanks for all the great information on your site Yves.
iv´e been building some of the modules you have there, and couldn´t be mor ehappy with them.

anyway i tried breadboarding the steiner filter today,
the Ca3096 version, at first it wasn´t working until i noticed on the datasheet of the ca3096 that in many of the circuits there, pin16(SUBSTRATE) was connected to ground or to the negtive voltage, so i tried connect pin 16 of the ca3096 to ground and then the filter seemed to be working, should it be connected this way ?
because i didn´t see anything about it in the schematic on your site.

i noticed on the datasheet of the ca3096 that in many of the circuits there, pin16(SUBSTRATE) was connected to ground or to the negtive voltage, so i tried connect pin 16 of the ca3096 to ground and then the filter seemed to be working, should it be connected this way ?
because i didn´t see anything about it in the schematic on your site.

thanks again,
Fridfinnur

Yes it is not mentioned on the schematics but I took care of this in the PCB design. if you have a look to the PCB drawing at my site you will see that the pin 16 (as well as all unused pin) is connected to the most negative point of the circuit (junction between R24, R25 and C7)._________________Yves

IT'S ALIVE! And it's really kicking! This is a really nice filter now it works. So stupid that I looked over that diode. But let's face it, if you stare to long at something, eventually you won't see the simple mistakes you made Thanks again!

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